It is known that on a commercial airplane, the position of the airplane is generally calculated on the basis of several types of positioning systems (or position generating means), in particular an Inertial Reference (IR) system, an Air Data Reference (ADR) system, and GNSS means which form part of a satellite positioning system of GNSS type (“Global Navigation Satellite System”). These GNSS means generally possess an integrity monitoring algorithm of RAIM type (“Receiver Autonomous Integrity Monitoring”) which makes it possible, by virtue of the redundancy of satellites, to determine the integrity of a calculated position. Moreover, the IR and ADR systems and the GNSS means are usually hybridized in the IR system, and this IR system generally comprises an algorithm of AAIM type (“Aircraft Autonomous Integrity Monitoring”) which makes it possible, by virtue of the different and complementary characteristics of these three IR, ADR and GNSS assemblies, to determine the integrity of a calculated position of the airplane. Errors or faults of a satellite forming part of the GNSS system can be detected and excluded in real time using these RAIM and AAIM algorithms.
Nevertheless, these RAIM and AAIM algorithms do not make it possible to detect (and to exclude) errors or faults of the systems onboard the airplane, that is to say the IR system, the ADR system or a customary receiver associated with the GNSS system. Now, such errors or faults may cause the calculation of an erroneous position of the airplane.